Self-compensating railway hand brake linkage

ABSTRACT

A railway car hand brake mechanism employing lever means and connecting linkages so constructed and arranged as to provide a multiplied braking force to the brake shoes. The multiplication factor remains substantially constant throughout the limits of movement of the mechanism.

O Unlted States Patent 1 1111 3,712,146

Sands 1 Jan. 23, 1973 SELF-CUMPENSATING RAILWAY [56] g f gi d 'Mm' n "IHAND BRAKE LINKAGE UNITED STATES PATENTS [75] (Me sands i 1,927,2379/1933 Klasing ..74/505 [73] Assignee: AMF Incorporated PrimaryExaminer-Milton Kaufman [22] led: March 1971 Attorney-George W. Priceand John H. Gallagher 21 Appl. No.: 127,211

, [57] ABSTRACT 52 us. Cl. ..74/491, 74/505, l88/33 A railway car handbrake mechanism employing lever [51 1m. 01. ..GOSg 7 02 means andConnecting linkages so constructed and [58] Field of Search ..74/51 1,505, 506, 507, 491; ranged as to provide a multiplied braking force tothe 183/49, 5 5 52, 53 55 33 brake shoes. The multiplication factorremains sub stantially constant throughout the limits of movement of themechanism.

7 Claims, 3 Drawing Figures 70 A SECOND BRA/(E SHOE MAI/(AGE; L 1

70A FIRST BRAKE o 5/ 05 LINKAGE BACKGROUND OF THE INVENTION Usually thehand wheel at one end of a car controls the brakes on the truck at thatend of the car only. As railway cars became larger and carried greaterloads, the braking force required to stop and hold the cars increasedsubstantially. Frequently, to stop or hold a railway car stationary, thehand brake wheel at only one end of the car is used. Thus, the brakes ofone truck only, not of both trucks, sometimes are used to hold a carstationary. With use, the brake shoes wear at different rates and it isnot uncommon that some brake shoes of a car function improperly. Underthese circumstances the braking force present to hold the railway car isseriously reduce, possibly to the point where the brakes are ineffectiveto hold a car.

SUMMARY OF THE INVENTION In this invention there is disclosed asimplified and reliable mechanism adapted to apply relatively largeforces to brake shoe linkages of a truck of a railway car. When usedwith two or more brake shoe linkages, the mechanism is self-compensatingto apply substantially equal braking forces to the two linkages. In thetruck of a railway car, a first brake shoe linkage is coupled to asecond brake shoe linkage through a chain that is looped around a pulleycarried by a traveling block. The chain assumes the shape of the letterU." Movement of the traveling block in a direction to cause a force intension within two arms of the U-shaped chain causes the pulley to rollalong the chain until the force transmitted from the block through eacharm of the U- shaped chain to each of the brake shoes is equal. Firstand second bell crank type levers connected to move in unison with eachother are interposed between a hand wheel and the traveling block.Turning of the hand wheel in a first direction shortens a pulley chainwhich is coupled to and urges the first and second crank levers to movesimultaneously in a first direction. The pulley chain and the cranklevers each multiply the force transmitted from the hand wheel and theincreased. force is coupled through the traveling block and the U-shapedchains to the brake shoes.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a side view of a railway hand brake linkage mechanismconstructed in accordance with the principles of this invention;

FIG. 2 is a top view of the structure illustrated in FIG. 1; and

FIG. 3 is an end view of the structure illustrated in FIG. 1.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION Referring in detail toFIGS. 1-3, a hand wheel 11 adapted for manual operation is rotatablycoupled through a shaft 12 to a gear box 14. Two plates 16 and 18positioned parallel to each other are secured to one end of the frame 20of the railway freight or tank car by welding or the like. The otherends of the parallel plates 16 and 18 are secured to and support thegear box 14.

Two support members 22 and 24 are positioned between and parallel toplates 16 and 18, and also are secured by welding or the like to theframe 20 of the railway car. Positioned below the gear box 14 andpivotally connected to plate 18 and support members 22 and 24 is a forceconverting means such as a double bell crank type of lever whichfunctions to transmit a force from a first direction to a seconddirection with increased magnitude. The double bell crank type of levercomprises a first bell crank type of lever 26 and a second bell cranktype of lever 28. The levers are rotatable about a common shaft 30 whichis supported by plates 18, 22, and 24. A pin 32 is supported between theouter extremities of the two levers 26 and 28 and supports a pulleyroller 34. Shaft 30 defines the fulcrum or pivot axis of the levers andpin 32 functions both as a shaft for pulley 34 and as a locking means tocause the levers 26 and 28 to move together.

A flexible member 33 such as a chain or the like is positioned aroundpulley 34. One end of chain 33 is anchored by a shackle 36 to aconnection plate 38 which is welded to plates 16 and 18. The other endof chain 33 is coupled to a shaft or the like in gear box 14 to be takenup or let out as the hand wheel 11 is rotated. It is seen that thearrangement of chain 33 and pulley 34 constitute a pulley mechanismwhich provides a mechanical advantage that multiplies the force appliedto levers 26 and 28 when chain 33 is drawn up by the rotation of handwheel 1 1.

Referring to levers 26 and 28, pin 40 connects a chain 42 to lever 26,and pin 44 couples a chain 46 to lever 28. It should be observed thatthe pins 40 and 44 are positioned closer to the fulcrum 30 than is theaxis of the pulley 34, thereby to provide an additional mechanicaladvantage in the operation of the levers. That is, since the pin 32 onwhich pulley roller 34 is mounted is further from fulcrum shaft 30 thanare the pins 40 and 44 on which chains 42 and 46 are mounted, the totalforce available at pins 40 and 44 for transmission to chains 42 and 46is greater than the force applied to pin 32 by chain 33.

As best seen in FIG. 1, the bell crank type of levers 26 and 28 eachhave a curved surface 35 which is convex in the general direction towardchains 42 and 46. When chain 33 is drawn up by the rotation of handwheel 11, levers 26 and 28 rotate in a counterclockwise direction aroundfulcrum 30 and the curved surfaces 35 progressively move downwardly ontop of chains 42 and 46, thus causing the portion of those chains whichextend between traveling block 48 and their points of contact withlevers 26 and 28 to continue to move in a horizontal direction as theyare pulled to the right.

It further is seen that when the levers 26 and 28 rotate in acounterclockwise direction the points where chains 42 and 46 firstcontact the levers progressively move around curved surfaces 35. Thecurvature of surface 35 is so chosen that the radial distance fromfulcrum 30 to the progressively changing points of first contact ofchains 42 and 46 remain substantially constant as levers 26 and 28rotate. The result of this feature is that the above discussedmechanical advantage achieved by the use of the levers remainssubstantially constant as a function of the angular rotation of thelevers.

As viewed in FIGS. 1 and 2, the left ends of the chains 42 and 46 areconnected to a self-compensating force distributing means such as atraveling block 48 which consists of two plates 50 and 52 positionedparallel to each other. The traveling block 48 supports two pins at theright end, one pin 54 for coupling chain 42 to the traveling block, andother pin 56 for coupling chain 46 to the traveling block. Positioned atthe left end of the traveling block is a pin 58 which rotatably supportsa pulley 60.

A shaft 62 extends upwardly from the traveling block 48 and through aslot 64, FIG. 2, in a horizontally extending support plate 66. Supportplate 66 is secured to the frame of the railway car. A relatively largeflat plate or washer 68 is secured to the upper end of the shaft 62 andthe lower surface of washer 68 is in sliding contact with the uppersurface of plate 66. Traveling block 48 can move freely back and forth,its path of travel being defined by the slot 64. It is to be noted thattraveling block 48 is not only free to move back and forth along ahorizontal path defined by slot 64 but also is free to pivot or rotateabout the vertical axis of shaft 62. Block 48 rotates about its shaft 62to take up any slack due to differences which may exist between thelengths of chain 42 and chain 46.

A chain 78 is looped around the pulley 60 of the traveling block and oneend of the chain is coupled to actuate a first brake shoe linkage andthe other end of the chain 78 is coupled to actuate a second brake shoelinkage. Chain 78 and pulley 60 are sized relative to each other topermit the chain to move freely over the pulley 60.

In the description of the operation which follows, it shall be assumedthat the hand brake structure is initially in a relaxed or no brakes oncondition. When the hand brakes of the railway freight or tank car areto be activated, the hand wheel 1 l is manually rotated in a clockwisedirection, for example, to set the brakes on a truck of the railway car.Referring specifically to FIG. 1, the end of the chain 33 coupledthrough the gear box 14 to the hand wheel is drawn up by being wrappedaround a driven shaft or the like to cause each of the two bell cranktype of levers 26 and 28 to rotate in a counterclockwise direction aboutthe fulcrum defined by common shaft 30. Rotation of the bell crank typeof levers 26 and 28 causes the links on the right ends of chains 42 and46 to be pulled towards the right, and in turn, causes the travelingblock 48 to move toward the right.

During operation of the bell crank type of levers it is to be noted thatthey move in unison and that they cQnvert a substantially verticallyapplied force and displacement to a horizontally applied force anddisplacement. In addition, as mentioned previously, the pulley mechanismprovided by chain 33 passing around pulley 34, and the arrangement ofthe chains 42 and 46 on levers 26 and 28 relative to the position ofpulley 34,

both provide respective mechanical advantages that result in a totalhorizontal pulling force on the brake shoe linkages that is greater thanthe force applied vertically by chain 33. Furthermore, the mechanicaladvantages remain substantially constant as the levers 26 and 28 rotateabout fulcrum 30.

The shaft 62 and flat plate 66, in cooperation with the slot 64 ofmember 66, permits the traveling block to move freely to the right.Additionally, the traveling block is free to rotate about thelongitudinal axis of shaft 62 to provide self compensation for slightdifference in lengths of the chain 42 and 46. Therefore, the forcetransmitted from each of the bell crank type of levers 26 and 28 to thetraveling block 48 is equally divided between the two chains 42 and 46.

Displacement of the traveling block toward the right causes the chain78, which is looped around the pulley 60 of the traveling block, to bepulled to the right. One end of the chain 78 pulls on a first brake shoelinkage to brake a first wheel or set of wheels and the other end of thechain 78 pulls on a second brake shoe linkage to brake a second wheel orset of wheels. It is to be noted that pulley 60 of traveling block 48 isfree to move along chain 78 to equalize the tension in each half portionof the chain and, therefore, the forces transmitted through each of thehalf portions of the chain are always equal.

It is to be understood that in the practice of the present invention itis not necessary that two bell crank type of levers 26 and 28, and twochains 42 and 46 be used. A single bell crank type of lever and a singlechain connected to traveling pulley 48 could be used without departingfrom the present invention so long as the applied forces and loads donot exceed the capabilities of the respective components.

What is claimed is:

1. In a railway car braking mechanism for applying braking force to oneor more brake shoes, the combination comprising brake shoe linkage forapplying a braking force to a brake shoe,

a crank type of lever having an arm which pivots about a fulcrum,

a pulley secured at an outward disposed portion of said lever,

means for connecting said brake shoe linkage to said lever at a radiallocation intermediate said fulcrum and said pulley,

elongated force transmitting means having at least a portion which isflexible and looped through said pulley and having one end fixedlysecured relative to said fulcrum,

force applying means connected to the other end of the elongated forcetransmitting means for applying to said pulley a force acting in asecond direction, thereby to rotate said lever about said fulcrum and toapply a greater force to the brake shoe linkage.

2. The combination claimed in claim 1 wherein said crank type of leverincludes a curved surface in the region thereof between the fulcrum andthe radial location where the brake shoe linkage is connected, at leasta portion of said curved surface having a substantially constant radiusof curvature relative to said fulcrum.

3. The combination claimed in claim 2 wherein said brake shoe linkage isflexible at least in the immediate portion thereof where it is connectedto the lever, whereby the flexible portion of said linkage progressivelycontacts and conforms to the curved surface of the lever as the lever isrotated about said fulcrum.

4. In a railway car braking mechanism for applying braking force to oneor more brake shoes, the combination comprising brake shoe linkage forapplying a force acting in a given direction to one or more brake shoes,

a bell crank type of lever having an arm which pivots about a fulcrumthat is fixed relative to the frame of said car,

a pulley secured at an outwardly disposed portion of the lever,

means including a first chain for connecting said brake shoe linkage tosaid lever at a radial location between said fulcrum and said pulley,

said lever having a curved surface in the region thereof between thefulcrum and said radial location where the brake shoe is connected, saidcurved surface being convex in the direction toward said first chain andat least a portion thereof having a substantially constant radius ofcurvature relative to said fulcrum,

force transmitting means including a second chain which is loopedthrough said pulley and has one end fixedly secured relative to thefulcrum,

force applying means connected to the other end of the second chain fordrawing the second chain around the pulley and thereby rotating saidlever about said fulcrum in a direction away from the first chain, saidsecond chain and pulley being arranged to provide a mechanical advantagethat multiplies the force that is applied at said other end of thesecond chain,

the connection of said first chain to said lever providing anothermechanical advantage which further multiplies the force applied to theother end of the secured chain.

5. The combination claimed in claim 4 wherein the means that includes afirst chain for connecting said brake shoe linkage to said lever furtherincludes a floating pulley block connected to the end of the first chainopposite to the end that is connected to said lever,

a third chain looped around said floating pulley block and having eachend connected to a respective brake shoe linkage.

6. In a railway car braking mechanism for applying substantially equalbraking forces to at least two brake shoes, the combination comprisingbrake shoe linkages, said curved surfaces being located ad acent thepositions where the chain linkages connect to the lever arms and havingat least portions thereof of substantially constant radii of curvaturerelative to the fulcrum, said curved surfaces being located closer tosaid fulcrum than the locations where the chain linkages are connectedto the lever arms,

a pulley attached to said lever arms at said outwardly disposedlocations,

a force transmitting chain secured at one end to the frame of the carand passing through the pulley in such a manner as to provide a forcemultiplying mechanical advantage when said chain transmits a force tothe lever means,

force applying means connected to the other end of the forcetransmitting chain to rotate said lever means and apply a pulling forceto the brake shoe linkage.

7. The combination claimed in claim 6 wherein said chain linkage forconnecting each brake shoe linkage to a respective lever arm includes,

1. In a railway car braking mechanism for applying braking force to oneor more brake shoes, the combination comprising brake shoe linkage forapplying a braking force to a brake shoe, a crank type of lever havingan arm which pivots about a fulcrum, a pulley secured at an outwarddisposed portion of said lever, means for connecting said brake shoelinkage to said lever at a radial location intermediate said fulcrum andsaid pulley, elongated force transmitting means having at least aportion which is flexible and looped through said pulley and having oneend fixedly secured relative to said fulcrum, force applying meansconnected to the other end of the elongated force transmitting means forapplying to said pulley a force acting in a second direction, thereby torotate said lever about said fulcrum and to apply a greater force to thebrake shoe linkage.
 2. The combination claimed in claim 1 wherein saidcrank type of lever includes a curved surface in the region thereofbetween the fulcrum and the radial location where the brake shoe linkageis connected, at least a portion of said curved surface having asubstantially constant radius of curvature relative to said fulcrum. 3.The combination claimed in claim 2 wherein said brake shoe linkage isflexible at least in the immediate portion thereof where it is connectedto the lever, whereby the flexible portion of said linkage progressivelycontacts and conforms to the curved surface of the lever as the lever isrotated about said fulcrum.
 4. In a railway car braking mechanism forapplying braking force to one or more brake shoes, the combinationcomprising brake shoe linkage for applying a force acting in a givendirection to one or more brake shoes, a bell crank type of lever havingan arm which pivots about a fulcrum that is fixed relative to the frameof said car, a pulley secured at an outwardly disposed portion of thelever, means including a first chain for connecting said brake shoelinkage to said lever at a radial location between said fulcrum and saidpulley, said lever having a curved surface in the region thereof betweenthe fulcrum and said radial location where the brake shoe is connected,said curved surface being convex in the direction toward said firstchain and at least a portion thereof having a substantially constantradius of curvature relative to said fulcrum, force transmitting meansincluding a second chain which is looped through said pulley and has oneend fixedly secured relative to the fulcrum, force applying meansconnected to the other end of the second chain for drawing the secondchain around the pulley and thereby rotating said lever about saidfulcrum in a direction away from the first chain, said second chain andpulley being arranged to provide a mechanical advantage that multipliesthe force that is applied at said other end of the second chain, theconnection of said first chain to said lever providing anothermechanical advantage which further multiplies the force applied to theother end of the secured chain.
 5. The combination claimed in claim 4wherein the means that includes a first chain for connecting said brakeshoe linkage to said lever further includes a floating pulley blockconnected to the end of the first chain opposite to the end that isconnected to said lever, a third chain looped around said floatingpulley block and having each end connected to a respective brake shoelinkage.
 6. In a railway car braking mechanism for applyingsubstantially equal braking forces to at least two brake shoes, thecombination comprising first and second brake shoe linkages for applyingrespective forces to said two brake shoes, double bell crank type oflever means having two lever arms rotatable together about a commonfulcrum that is fixed relative to the frame of said car, means includingrespective chain linkage for connecting each brake shoe linkage to arespective lever arm at a location thereon between said fulcrum and anoutwardly disposed location, said lever means having two surfaces thatare convexly curved in a general direction toward the brake shoelinkages, said curved surfaces being located adjacent the positionswhere the chain linkages connect to the lever arms and having at leastportions thereof of substantially constant radii of curvature relativeto the fulcrum, said curved surfaces being located closer to saidfulcrum than the locations where the chain linkages are connected to thelever arms, a pulley attached to said lever arms at said outwardlydisposed locations, a force transmitting chain secured at one end to theframe of the car and passing through the pulley in such a manner as toprovide a force multiplying mechanical advantage when said chaintransmits a force to the lever means, force applying means connected tothe other end of the force transmitting chain to rotate said lever meansand apply a pulling force to the brake shoe linkage.
 7. The combinationclaimed in claim 6 wherein said chain linkage for connecting each brakeshoe linkage to a respective lever arm includes, a floating pulley blockhaving respective linkages connected to the two lever arms, a U-shapedchain looped through said pulley block and having its two endsrespectively connected to said first and second brake shoe linkages.